1. Field of Use
This invention relates to apparatus for watering and draining soil in deserts and dry areas to provide for control of plant and tree growth in such areas, and the invention is more particularly concerned with apparatus that can be used interchangeably for either watering or draining an area in which the apparatus is installed, and with installations comprising such apparatus.
2. Prior Art
One arrangement heretofore proposed for either watering or draining an area of soil in accordance with prevailing requirements is disclosed in U.S. Pat. No. 3,461,675. In this system, a trench in the area to be treated has a water-impermeable lining, and a closed-meshed duct system extends through the area. Although both irrigation and draining can be accomplished with it, the arrangement is expensive because it necessitates a great amount of excavation work for emplacement of the trench lining.
Another prior irrigation arrangement, disclosed in U.S. Pat. No. 3,698,195, comprises two ducts, one inside the other, both of which are sufficiently resilient to permit the two-duct conduit to be rolled up along its length. While offering convenience in transportation and in manipulation during emplacement and removal, this apparatus can be used only for pressure watering, owing to the relatively small space between the ducts and the suppleness of the inner duct, which retains its cross-section form only under the force of pressurized water in its interior.
U.S. Pat. No. 3,672,571 discloses a conduit comprising primary and secondary ducts, which conduit can likewise be used only for pressure watering. Although not so supple as to be readily flattened, the primary duct, to which irrigation water is supplied, has restricted outlets that reduce the pressure of the supplied water so that it enters the adjacent soil as a plurality of low pressure trickles or drips. Because these outlets are restricted, the apparatus is not suitable for use in draining and dewatering.
In contrast to these prior arrangements, it is the general object of the present invention to provide simple and inexpensive apparatus by which either watering or drainage of an area of soil can be accomplished, in accordance with prevailing needs, and which operates substantially by natural circulation both for watering and for drainage.
It is also an object of this invention to provide a double-duct conduit that is inexpensive in itself and can be emplaced in an area to be irrigated and/or drained at relatively low cost and with a minimum of digging.
Another and more specific object of the invention is to provide apparatus of the character described which, when used for irrigation or watering, provides for entry of water into the adjacent soil in a trickle of sufficiently low pressure not to cause washing away or shifting of portions of the soil, but which is nevertheless capable of being employed for drainage or dewatering without the need for any adjustment or modification.